trans-3,5,4'-Trihydroxystilbene (trans-resveratrol) is a phytochemical present in peanuts, grapes and wine with beneficial effects such as protection against cardiovascular disease and cancer prevention. The purpose of this study was to evaluate whether high doses of trans-resveratrol have harmful effects on Sprague-Dawley rats. trans-Resveratrol was administered orally to male rats for 28 d at a dose of 20 mg/(kg x d), 1000 times the amount consumed by a 70-kg person taking 1.4 g of trans-resveratrol/d. Body weight, and food and water consumption did not differ between rats treated with trans-resveratrol and the control group. Hematologic and biochemical variables were not affected by the treatment. Histopathologic examination of the organs obtained at autopsy did not reveal any alterations. These results support the view that repeated consumption of trans-resveratrol at 20 mg/(kg x d) does not adversely affect the variables tested in rats.